Tuesday, 16 March 2010

Speciation: still one of nature’s great mysteries

First of all a disclaimer: I’m a self-confessed dilettante, not a real philosopher, and, even though I read widely and take an interest in all sorts of things scientific, I’m not a scientist either. I know a little bit more about physics and mathematics than I do biology, but I can say with some confidence that evolution, like consciousness and quantum mechanics, is one of nature’s great mysteries. But, like consciousness and quantum mechanics, just because it’s a mystery doesn’t make it any less real. Back in Nov.07, I wrote a post titled: Is evolution fact? Is creationism myth?

First, I defined what I meant by ‘fact’: it’s either true or false, not something in between. So it has to be one or the other: like does the earth go round the sun or does the sun go round the earth? One of those is right and one is wrong, and the one that is right is a fact.

Well, I put evolution into that category: it makes no sense to say that evolution only worked for some species and not others; or that it occurred millions of years ago but doesn’t occur now; or the converse that it occurs now, but not in the distant past. Either it occurs or it never occurred, and all the evidence, and I mean all of the evidence, in every area of science: genetics, zoology, palaeontology, virology; suggests it does. There are so many ways that evolution could have been proven false in the last 150 years since Darwin’s and Wallace’s theory of natural selection, that it’s just as unassailable as quantum mechanics. Natural selection, by the way, is not a theory, it’s a law of nature.

Now, both proponents and opponents of evolutionary theory often make the mistake of assuming that natural selection is the whole story of evolution and there’s nothing else to explain. So I can confidently say that natural selection is a natural law because we see evidence of it everywhere in the natural world, but it doesn’t explain speciation, and that is another part of the story that is rarely discussed. But it’s also why it’s one of nature’s great mysteries. To quote from this week’s New Scientist (13 March, 2010, p.31): ‘Speciation still remains one of the biggest mysteries in evolutionary biology.’

This is a rare admission in a science magazine, because many people believe, on both sides of the ideological divide (that evolution has created in some parts of the world, like the US) that it opens up a crack in the scientific edifice for creationists and intelligent design advocates to pull it down.

But again, let’s compare this to quantum mechanics. In a recent post on Quantum Entanglement (Jan.10), where I reviewed Louisa Gilder’s outstanding and very accessible book on the subject, I explain just how big a mystery it remains, even after more than a century of experimentation, verification and speculation. Yet, no one, whether a religious fundamentalist or not, wants to replace it with a religious text or any other so-called paradigm or theory. This is because quantum mechanics doesn’t challenge anything in the Bible, because the Bible, unsurprisingly, doesn’t include anything about physics or mathematics.

Now, the Bible doesn’t include anything about biology either, but the story of Genesis, which is still a story after all the analysis, has been substantially overtaken by scientific discoveries, especially in the last 2 centuries.

But it’s because of this ridiculous debate, that has taken on a political force in the most powerful and wealthy nation in the world, that no one ever mentions that we really don’t know how speciation works. People are sure to counter this with one word, mutation, but mutations and genetic drift don’t explain how genetic anomalies amongst individuals lead to new species. It is assumed that they accumulate to the point that, in combination with natural selection, a new species branches off. But the New Scientist cover story, reporting on work done by Mark Pagel (an evolutionary biologist at the University of Reading, UK) challenges this conventionally held view.

To quote Pagel: “I think the unexamined view that most people have of speciation is this gradual accumulation by natural selection of a whole lot of changes, until you get a group of individuals that can no longer mate with their old population.”

Before I’m misconstrued, I’m not saying that mutation doesn’t play a fundamental role, as it obviously does, which I elaborate on below. But mutations within individuals don’t axiomatically lead to new species. This is a point that Erwin Schrodinger attempted to address in his book, What is Life? (see my review posted Nov.09).

Years ago, I wrote a letter to science journalist, John Horgan, after reading his excellent book The End of Science (a collection of interviews and reflections by some of the world’s greatest minds in the late 20th Century). I suggested to him an analogy between genes and environment interacting to create a human personality, and the interaction between speciation and natural selection creating biological evolution. I postulated back then that we had the environment part, which was natural selection, but not the gene part of the analogy, which is speciation. In other words, I suggested that there is still more to learn, just like there is still more to learn about quantum mechanics. We always assume that we know everything that there is to know, when clearly we don’t. The mystery inherent in quantum mechanics indicates that there is something that we don’t know, and the same is true for evolution.

Mark Pagel’s research is paradigm-challenging, because he’s demonstrated statistically that genetic drift by mutation doesn’t give the right answers. I need to explain this without getting too esoteric. Pagel looked at the branches of 101 various (evolutionary) trees, including: ‘cats, bumblebees, hawks, roses and the like’. By doing a statistical analysis of the time between speciation events (the length of the branches) he expected to get a Bell curve distribution which would account for the conventional view, but instead he got an exponential curve.

To quote New Scientist: ‘The exponential is the pattern you get when you are waiting for some single, infrequent event to happen… the length of time it takes a radioactive atom to decay, and the distance between roadkills on a highway.’

In other words, as the New Scientist article expounds in some detail, new species happen purely by accident. What I found curious about the above quote is the reference to ‘radioactive decay’ which was the starting point for Erwin Schrodinger’s explanation of mutation events, which is why mutation is still a critical factor in the whole process.

Schrodinger went to great lengths, very early in his exposition, to explain that nearly all of physics is statistical, and gave examples from magnetism to thermal activity to radioactive decay. He explained how this same statistical process works in creating mutations. Schrodinger coined a term, ‘statistico-deterministic’, but in regard to quantum mechanics rather than physics in general. Nevertheless, chaos and complexity theory reinforce the view that the universe is far from deterministic at almost every level that one cares to examine it. As the New Scientist article argues, Pagel’s revelation supports Stephen Jay Gould’s assertion: ‘that if you were able to rewind history and replay the evolution on Earth, it would turn out differently every time.’

I’ve left a lot out in this brief exposition, including those who challenge Pagel’s analysis, and how his new paradigm interacts with natural selection and geographical separation, which are also part of the overall picture. Pagel describes his own epiphany when he was in Tanzinia: ‘watching two species of colobus monkeys frolic in the canopy 40 metres overhead. “Apart from the fact that one is black and white and one is red, they do all the same things... I can remember thinking that speciation was very arbitrary. And here we are – that’s what our models are telling us.”’ In other words, natural selection and niche-filling are not enough to explain diversification and speciation.

What I find interesting is that wherever we look in science, chance plays a far greater role than we credit. It’s not just the cosmos at one end of the scale, and quantum mechanics at the other end, that rides on chance, but evolution, like earthquakes and other unpredictable events, also seems to be totally dependent on the metaphorical roll of the dice.

Addendum 1 : (18 March 2010)

Comments posted on New Scientist challenge the idea that a ‘bell curve’ distribution should have been expected at all. I won’t go into that, because it doesn’t change the outcome: 78% of ‘branches’ statistically analysed (from 110) were exponential and 0% were normal distribution (bell curve). Whatever the causal factors, in which mutation plays a definitive role, speciation is as unpredictable as earthquakes, weather events and radio-active decay (for an individual isotope).

Addendum 2: (18 March 2010)

Writing this post, reminded me of Einstein’s famous quote that ‘God does not play with dice’. Well, I couldn’t disagree more. If there is a creator-God (in the Einstein mould) then first and foremost, he or she is a mathematician. Secondly, he or she is a gambler who loves to play the odds. The role of chance in the natural world is more fundamental and universally manifest than we realise. In nature, small variances can have large consequences: we see that with quantum theory, chaos theory and evolutionary theory. There appears to be little room for determinism in the overall play of the universe.